The present invention generally relates to implantable stimulator systems, and more particularly relates to an implantable stimulator system utilizing one or more implantable microstimulators for treating epilepsy.
Epilepsy is characterized by a tendency to recurrent seizures that can lead to loss of awareness, loss of consciousness, and/or disturbances of movement, autonomic function, sensation (including vision, hearing and taste), mood, and/or mental function. Epilepsy afflicts 1-2% of the population in the developed world. The mean prevalence of active epilepsy (i.e., continuing seizures or the need for treatment) in developed and undeveloped countries combined is estimated to be 7 per 1,000 of the general population, or approximately 40 million people worldwide. Studies in developed countries suggest an annual incidence of epilepsy of approximately 50 per 100,000 of the general population. However, studies in developing countries suggest this figure is nearly double at 100 per 100,000.
Epilepsy is often but not always the result of underlying brain disease. Any type of brain disease can cause epilepsy, but not all patients with the same brain pathology will develop epilepsy. The cause of epilepsy cannot be determined in a number of patients; however, the most commonly accepted theory posits that it is the result of an imbalance of certain chemicals in the brain, e.g., neurotransmitters. Children and adolescents are more likely to have epilepsy of unknown or genetic origin. The older the patient, the more likely it is that the cause is an underlying brain disease such as a brain tumor or cerebrovascular disease.
Trauma and brain infection can cause epilepsy at any age, and in particular, account for the higher incidence rate in developing countries. For example, in Latin America, neurocysticercosis (cysts on the brain caused by tapeworm infection) is a common cause of epilepsy; in Africa, AIDS and its related infections, malaria and meningitis, are common causes; in India, AIDS, neurocysticercosis and tuberculosis, are common causes. Febrile illness of any kind, whether or not it involves the brain, can trigger seizures in vulnerable young children, which seizures are called febrile convulsions. About 5% of such children go on to develop epilepsy later in life. Furthermore, for any brain disease, only a proportion of sufferers will experience seizures as a symptom of that disease. It is therefore suspected that those who do experience such symptomatic seizures are more vulnerable for similar biochemical/neurotransmitter reasons.
The invention disclosed and claimed herein provides means for chronically stimulating a trigeminal ganglion or ganglia, a trigeminal nerve(s), or branch(es) of a trigeminal nerve(s) with a miniature implantable neurostimulator that can be implanted with a minimal surgical procedure. This invention also provides means for chronically stimulating a greater occipital nerve(s), lesser occipital nerve(s), third occipital nerve(s), facial nerve(s), glossopharyngeal nerve(s), or a branch(es) of any of these neural structures with a miniature implantable neurostimulator that can be implanted with a minimal surgical procedure. Electrical stimulation of such targets may provide significant therapeutic benefit in the management of epilepsy.
To treat epilepsy, a miniature implantable neurostimulator, such as a Bionic Neuron (also referred to as a BION(trademark) microstimulator) may be implanted via a minimal surgical procedure (e.g., injection or small incision) adjacent to a trigeminal ganglion or ganglia, trigeminal nerve(s), branch(es) of a trigeminal nerve(s) (e.g., ophthalmic nerve(s), maxillary nerve(s), and/or mandibular nerve(s)), or branch(es) of any of these neural structures. A BION may additionally or alternatively be implanted adjacent to a greater occipital nerve(s), a lesser occipital nerve(s), a third occipital nerve(s), a facial nerve(s), a glossopharyngeal nerve(s), or a branch(es) of any of these neural structures to treat epilepsy.
A microstimulator may be implanted via injection and/or via endoscopic means. A more complicated surgical procedure may be required for sufficient access to a particular nerve (e.g., a nerve surrounded by scar tissue) or for purposes of fixing the neurostimulator in place. A single microstimulator may be implanted, or two or more microstimulators may be implanted to achieve greater stimulation of one or more nerves.
The microstimulator used with the present invention possesses one or more of the following properties, among others:
at least two electrodes for applying stimulating current to surrounding tissue;
electronic and/or mechanical components encapsulated in a hermetic package made from biocompatible material(s);
an electrical coil or other means of receiving energy and/or information inside the package, which receives power and/or data by inductive or radio-frequency (RF) coupling to a transmitting coil placed outside the body, thus avoiding the need for electrical leads to connect devices to a central implanted or external controller;
means for receiving and/or transmitting signals via telemetry;
means for receiving and/or storing electrical power within the microstimulator; and
a form factor making the microstimulator implantable via a minimal surgical procedure.
A microstimulator may operate independently, or in a coordinated manner with other implanted devices, or with external devices. For instance, a microstimulator may incorporate means for sensing epilepsy, which it may then use to control stimulation parameters in a closed loop manner. The sensing and stimulating means may be incorporated into a single microstimulator, or a sensing means may communicate sensed information to at least one microstimulator with stimulating means.